Toxicological effects of pyrethroids on non-target aquatic insects

Bioaccumulation of Deltamethrin and Piperonyl butoxide in Labeo rohita fish

Deltamethrin (DLM), in combination with the synergist piperonyl butoxide (PBO), is extensively used in pest control programs due to its potent pesticidal properties and appreciable safety margin. However, various research studies report their adverse effects on non-target organisms. In this study, we investigated the toxicity of DLM, PBO, and a DLM-PBO (3:1) combination on Labeo rohita (L. rohita) fish fingerlings. Fish behavior and mortality rates were recorded at different time intervals up to 96 h for concentrations of 0.003, 0.007, 0.015, 0.031, and 0.062 µg/mL, respectively. Biochemical, hematological, and histopathological studies were carried out. High-performance liquid chromatography (HPLC) was used to detect and quantify residues in fish samples. The LC50 values after 48 h for DLM, PBO, and DLM-PBO exposed fish fingerlings were found to be 0.028, 0.066, and 0.007 µg/mL, respectively. At a concentration of 0.003 µg/mL of DLM, PBO, and DLM-PBO, the treated fish fingerlings exhibited similar behavior to the control group. Hematological parameters, such as red blood cell (RBC) and white blood cell (WBC) counts, were reduced in the treated groups compared to the control. Biochemical parameters showed increased levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), while total serum protein levels decreased in DLM, PBO, and DLM-PBO treated fingerlings. Histopathological examination of liver, gill, and heart tissues revealed lesions with hydropic degeneration in the liver and fusions of gill lamellae in the treated tissues. Fish fingerlings exposed to the DLM-PBO combination appeared highly prone to toxicity compared to those treated with DLM and PBO separately.

Temperature-dependent in vitro hepatocytotoxicity of insecticides in bats

Heterothermic insectivorous bats are supposed to experience differential adverse effects of insecticidal pollutants depending on their seasonal and/or daily variation of metabolic and detoxification rates. Here, we investigated effects of imidacloprid, cypermethrin and fipronil on Nyctalus noctula bat-derived hepatocytes through cytotoxicity, cell inhibition and death at different concentrations (0.01, 0.1, 1, 10, 100, 1000 μg/ml), exposure times (10, 24, 48 hrs), incubation temperatures simulating hibernation (8 °C), daily torpor (20 °C), normothermy (37 °C) and active flight (40 °C), and cytochrome P450 addition. Toxic effects were significantly influenced by temperature (p < 0.05), with strong cytotoxicity after 10 hour exposure to fipronil or cypermethrin at 37 and 40 °C, cell replication inhibition (all insecticides at 8 °C) and cellular stimulation, with slight culture proliferation after 48 hours (all insecticides at 40 °C). Replacing protected chiropterans with cell cultures is a way to assess and extrapolate risks of insecticides for bats.

Respiratory system: Highly exposed yet under-reported organ in pyrethrin and pyrethroid toxicity

Pyrethrin and pyrethroid are a relatively new class of pesticides with potent insecticidal properties. Pyrethrins are naturally occurring pesticides obtained from the Chrysanthemum cinerariaefolium flower, while pyrethroids are their synthetic derivatives. They are widely used as the insecticides of choice in agriculture, veterinary medicine, public health programs, and household activities. Pyrethrin, being a broad-spectrum insecticide kills a wide range of pests, while pyrethroids last longer in the environment owing to low susceptibility to sunlight, and greater stability and efficacy than parent molecules. Humans can be exposed through inhalation, ingestion, and dermal routes. Indoor usage of an insecticide poses a serious risk to human health, especially to women, children, and stay-at-home people. Although pyrethrin and pyrethroid are generally considered safe, sustained skin or inhalation exposure or direct contact with open wounds results in higher toxicity to mammals. There is a paucity of data on the impact of pyrethrin and pyrethroid on overall pulmonary health. The respiratory system, from the nose, nasal passages, airways, and bronchi to the pulmonary alveoli, is vulnerable to environmental contaminants such as pesticides because of its anatomical location as well as being a highly blood profused organ. Under and over-functioning of the respiratory system triggers diverse pathologies such as serious infections, allergies, asthma, metastatic malignancies, and auto-immune conditions. While the association between workplace-related pesticide exposures and respiratory diseases and symptoms is well documented, it is important to understand the adverse health impact of pyrethrin and pyrethroid on the general population for awareness and also for better regulation and implementation of the law.

A proposal to reduce the amount of permethrin entering wastewater resultant from topical use to treat scabies

The incidence of scabies is rising in the last years. Subsequently, the use of pharmaceuticals to treat the disease has also increased. Treatment with topical permethrin is usually recommended as a first line agent. This substance is also an aquatic contaminant that is toxic for many non-target organisms, and has been included as a priority substance in the recently published proposal of the European Water Framework Directive. Current guidelines neglect the potential environmental impact of this drug, recommending that the cream should be applied head to toe and "washed off after 8-12 h". Recently, a wiping procedure before hand washing after application of the topical treatment resulted in a 66 % reduction of the amount of diclofenac released in wastewater. The authors suggested that this method could be explored for other topical treatments. In the case of scabiosis, a protocol implicating the whole body needs to be designed. The absorption of topical permethrin is low. Considering the growing incidence of scabies, the amount of the pyrethroid reaching the environment may also be increasing. Therefore, we believe that applying the wiping procedure to the case of topical permethrin deserves consideration. Other measures to minimize the amount of permethrin residues reaching wastewater by washing clothes and bed linen such as wearing single-use pijamas should also be explored. In conclusion, we need to apply a One Health approach in the treatment with scabies, without neglecting the environmental impact of pharmaceuticals. It is not rational to forget drugs once they go down the drain.

Spatiotemporal distancing of crops reduces pest pressure while maintaining conservation biocontrol in oilseed rape

BACKGROUND

Agricultural landscapes provide resources for arthropod pests as well as their natural enemies. To develop integrated pest management (IPM) practices, it is important to understand how spatiotemporal location influences crop colonization and damage severity. We performed a 3-year (2016-2018) field experiment in winter oilseed rape (OSR, Brassica napus) fields in Estonia, where half of the fields were within 500 m of the location of the previous year's winter OSR field and half were outside this zone. We investigated how distance from the previous year's OSR crop influences the infestation and parasitism rates of two of its most important pests: the pollen beetle (Brassicogethes aeneus) and the cabbage seed weevil (Ceutorhynchus obstrictus).

RESULTS

When the distance from the previous year's OSR crop was >500 m, we recorded significantly reduced pest pressure by both B. aeneus and C. obstrictus in the study fields. Biocontrol of both pests, provided by parasitic wasps, was high in each study year and commonly not affected by distance. Mean parasitism rates of B. aeneus were >31%, occasionally reaching >70%; for C. obstrictus, mean parasitism was >46%, reaching up to 79%, thereby providing effective biocontrol for both pest species.

CONCLUSION

Spatiotemporal separation of OSR fields can reduce pest pressure without resulting in reduced parasitism of OSR pests. This supports a spatiotemporal field separation concept as an effective and sustainable technique for IPM in OSR. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Use of insect pest thresholds in oilseed rape and cereals: is it worth it?

BACKGROUND

Integrated pest management (IPM) uses thresholds to minimize pesticide use, and field monitoring of damaging organisms is an important component to evaluate whether or not thresholds have been breached. However, monitoring requires time and knowledge which impacts costs and benefits. In this study, we evaluated the effects of using insect pest thresholds on time effort, frequency of insecticide treatment and economics in comparison with common farm practices (business as usual) in winter wheat (WW), winter barley (WB) and winter oilseed rape (OSR). This study was done over 2 years (2018 to 2020) on 24 conventionally managed farms in North Rhine-Westphalia (Germany).

RESULTS

Farmers spent significantly more time (42 min ha-1/season) monitoring insect pests in OSR than in WW (16 min ha-1/season) and WB (19 min ha-1/season). The use of insecticides in OSR was significantly reduced by 42% in comparison to business as usual. In cereal crops, the use of insecticide treatment was reduced by 50% but this was not significantly different to business as usual. Yields were not significantly reduced when crops were managed in accordance with IPM, and negative differences were small and not significant. However, economically, the costs of monitoring can only be recovered when labor costs and commodity prices are low and insecticide cost is high.

CONCLUSION

Insect pest thresholds can help link the policy and environmental goals of insecticide reduction and the agronomic goal of production security. In the future, the time and cost required for monitoring should be reduced through intelligent solutions and tools, increasing the economic viability of monitoring and IPM. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

High-efficiency removal of pyrethroids using a redesigned odorant binding protein

Pyrethroids are ubiquitously present in environmental media and threaten both the ecosystem and human health. To explore effective ways to remove pyrethroids from the environment, an odorant binding protein (OBP) with affinity for various pyrethroids was investigated. Initially, the target OBP, Spodoptera littoralis pheromone binding protein 1 (SlitPBP1), underwent redesign to enhance its affinity for pyrethroids. The modified SlitPBP1E97ND106E demonstrated a substantially increased affinity for deltamethrin (DeltaM), with a dissociation constant of 0.77 ± 0.17 μM. The affinity of SlitPBP1E97ND106E for other pyrethroids also increased to varying extents. Consequently, SlitPBP1E97ND106E displayed a markedly enhanced capability to adsorb and remove pyrethroids. When exposed to free SlitPBP1E97ND106E in solution, the reduction in DeltaM surged from 16.78 ± 0.32% to 97.51 ± 0.56%. SlitPBP1E97ND106E was immobilized by coupling the protein to Ni2+-NTA agarose resin. Liquid chromatography results attested to the superior efficacy of immobilized SlitPBP1E97ND106E in removing pyrethroids, especially DeltaM. No significant differences in pyrethroid removal were detected across various water samples. Our findings introduce a potent tool for pyrethroid removal. A wider range of OBPs can similarly be optimized and applied to remove organic pollutants, including but not limited to pesticides.

The water-exiting behavior and survival of predaceous diving beetles in responses to lambda-cyhalothrin, chlorantraniliprole, and thiamethoxam

Predaceous diving beetles (dytiscids) are important top insect predators in various natural, agricultural, and artificial water bodies. How they respond to human disturbances such as insecticide contamination to their habitats has been understudied. In this study, we investigated the lethal effects of lambda-cyhalothrin, chlorantraniliprole, and thiamethoxam at nominal field concentrations in 3 cm-deep water in a hypothetical paddy field (Ci,3) on adult Dytiscus sinensis Feng (Coleoptera: Dytiscidae). Lambda-cyhalothrin exhibited significant lethal effects on D. sinensis adults with its Ci,3 exceeding the 95 % confidence interval lower limits for 24, 48, 72, and 96 h- LC99. Chlorantraniliprole and thiamethoxam showed no significant lethal effects on D. sinensis adults at their respective Ci,3 at 24, 48, or 72 h. Additionally, we assessed the temporal propensity of D. sinensis adults to exit water contaminated with chlorantraniliprole and thiamethoxam, respectively. There were significantly more individuals that temporally exited the chlorantraniliprole-contaminated water than clean water 30 min after placing a tile island in the test arena. Meanwhile, thiamethoxam-contaminated water did not repel significantly more individuals than clean water when observed at 10, 30, or 60 min. The study highlights the availability and importance of selecting safer insecticides for dytiscid conservation in agricultural and adjacent habitats, considering the potential of these water bodies becoming ecological traps that keep attracting and killing aquatic beneficials. The water-exiting behavior found indicates the capability of some wildlife to effectively avoid further exposure to toxicants.

Comparative effectiveness of biorational pesticides for management of Phenacoccus solenopsis Tinsley and Paracoccus marginatus Williams & Granara de Willink in Gymnema sylvestre (Retz.) R.Br. ex Sm

The cotton mealybug, Phenacoccus solenopsis Tinsley and papaya mealybug, Paracoccus marginatus Williams and Granara de Willink (Hemiptera: Pseudococcidae) are becoming major threats to the production of Gymnema sylvestre R. Br. (Asclepiadaceae) in India. Management mainly depends on chemical insecticides which cause a serious problem of pesticide residue and insecticide resistance. The use of biorational insecticides such as biopesticides, botanicals, insect growth regulators, and microbial insecticides is important components of an Integrated Pest Management (IPM) program for successful management. We evaluated the bio-efficacy of twelve biorational insecticides, including entomopathogenic fungi (EPF), using the leaf spray method in laboratory conditions at 25 ± 1 °C, 70 % ± 5 % RH. The results revealed that the highest percent mortality was recorded by acetamiprid 20 % SP (100.00 %), followed by azadirachtin (98.27 %), Lecanicillium muscarium (2 × 109 spores/mL) (85.70 %) and Ocimum sanctum leaf extract (76.87 %) at 120 h after treatment (HAT) in P. solenopsis. In P. marginatus, 100.00 %, 96.39 % and 85.67 % and 74.90 % mortalities were achieved by acetamiprid 20 % SP, azadirachtin, L. muscarium (2 × 109 spores/mL) and O. sanctum leaf extract, respectively, at 120 HAT during the first spray. Various biorational insecticides showed a more or less similar trend of percent mortality in both species during the second spray. In both species, the lowest percent mortality was recorded by Andrographis paniculata leaf extract (46.29, 44.54) and (41.03, 46.39) at 120 Hours after treatment in the first and second spray, respectively. It was concluded that all the prescribed treatments are more effective than the control. Overall, azadirachtin recorded the highest percent mortality after acetamiprid and had the shortest LT50 (12.52 h) and (13.87 h) values in P. solenopsis and P. marginatus, respectively. Our study emphasizes that biopesticides like Azadirachtin 1 % EC (10000 ppm), L. muscarium (2 × 109 spores/mL) (5 mL/L) and O. sanctum leaf extract (5 %) may be recommended as alternatives to synthetic insecticides. Botanicals and EPF would be the most effective approach for sustainable integrated management of P. solenopsis and P. marginatus in the G. sylvestre ecosystem.

Chlorpyrifos toxicity and detoxifying enzymes activities in three native-aquatic species of macroinvertebrates from an agricultural area

Non-target species from agricultural areas might be exposed to sublethal pesticide concentrations favoring survival and reproduction of the resistance individuals. The objective of this study was to evaluate chlorpyrifos toxicity and detoxification enzymatic activities on three species (Hyalella curvispina, Heleobia parchappii and Girardia tigrina) from a drain channel with history of insecticide contamination (EF) and the Neuquén river (NR) in Argentina. Chlorpyrifos toxicity on amphipods (H. curvispina) and planarians (G. tigrina) from NR was about six- and two-fold higher than that of their counterparts from EF. Mean carboxylesterases (CarE) activities determined in the three species from NR were significantly different from EF, whereas mean glutathione-S-transferase (GST) activities were no significantly different. Finally, planarians from EF showed significantly higher mean 7-ethoxycoumarine O-deethylase (ECOD) activity than those from NR. Amphipods from both sites displayed similar ECOD activities. The present results suggest that chlorpyrifos resistance in amphipods from EF is not conferred by increased detoxification.

Venoms with oral toxicity towards insects

Animal venoms are a promising source of potential bioinsecticides. To find hits with pronounced oral insect toxicity, we screened 82 venoms using Achroia grisella (Lepidoptera) and Tenebrio molitor (Coleoptera) larvae, and adult Drosophila melanogaster (Diptera). We also injected the most potent venoms in adult D. melanogaster to compare their efficiency in different routes of administration. 18 venoms from spiders and snakes show high oral toxicity and can be further exploited to isolate new insecticides.

Acute sublethal exposure to ethiprole impairs physiological and oxidative status in the Neotropical fish Astyanax altiparanae

Ethiprole, a phenylpyrazole insecticide, has been increasingly used in the Neotropical region to control stink bug pests in soybean and maize fields. However, such abrupt increases in use may have unintended effects on non-target organisms, including those inhabiting freshwater ecosystems. Here, we evaluated the effects of acute (96 h) sublethal exposure to ethiprole (up to 180 μg/L, which is equivalent to 0.013% of the recommended field dose) on biomarkers of stress in the gills, liver, and muscle of the Neotropical fish Astyanax altiparanae. We further recorded potential ethiprole-induced effects on the structural histology of A. altiparanae gills and liver. Our results showed that ethiprole exposure increased glucose and cortisol levels in a concentration-dependent manner. Ethiprole-exposed fish also exhibited higher levels of malondialdehyde and greater activity of antioxidant enzymes, such as glutathione-S-transferase and catalase, in both gills and liver. Furthermore, ethiprole exposure led to increased catalase activity and carbonylated protein levels in muscle. Morphometric and pathological analyses of the gills revealed that increasing ethiprole concentration resulted in hyperemia and loss of integrity of the secondary lamellae. Similarly, histopathological analysis of the liver demonstrated higher prevalence of necrosis and inflammatory infiltrates with increasing ethiprole concentration. Altogether, our findings demonstrated that sublethal exposure to ethiprole can trigger a stress response in non-target fish species, which may lead to potential ecological and economic imbalances in Neotropical freshwater systems.

Unintended consequences: Disrupting microbial communities of Nilaparvata lugens with non-target pesticides

Insects are frequently exposed to a range of insecticides that can alter the structure of the commensal microbiome. However, the effects of exposure to non-target pesticides (including non-target insecticides and fungicides) on insect pest microbiomes are still unclear. In the present study, we exposed Nilaparvata lugens to three target insecticides (nitenpyram, pymetrozine, and avermectin), a non-target insecticide (chlorantraniliprole), and two fungicides (propiconazole and tebuconazole), and observed changes in the microbiome's structure and function. Our results showed that both non-target insecticide and fungicides can disrupt the microbiome's structure. Specifically, symbiotic bacteria of N. lugens were more sensitive to non-target insecticide compared to target insecticide, while the symbiotic fungi were more sensitive to fungicides. We also found that the microbiome in the field strain was more stable under pesticides exposure than the laboratory strain (a susceptible strain), and core microbial species g_Pseudomonas, s_Acinetobacter soli, g_Lactobacillus, s_Metarhizium minus, and s_Penicillium citrinum were significantly affected by specifically pesticides. Furthermore, the functions of symbiotic bacteria in nutrient synthesis were predicted to be significantly reduced by non-target insecticide. Our findings contribute to a better understanding of the impact of non-target pesticides on insect microbial communities and highlight the need for scientific and rational use of pesticides.

Conservation and Targets of miR-71: A Systematic Review and Meta-Analysis

MicroRNAs (miRNAs) perform a pivotal role in the regulation of gene expression across the animal kingdom. As negative regulators of gene expression, miRNAs have been shown to function in the genetic pathways that control many biological processes and have been implicated in roles in human disease. First identified as an aging-associated gene in C. elegans, miR-71, a miRNA, has a demonstrated capability of regulating processes in numerous different invertebrates, including platyhelminths, mollusks, and insects. In these organisms, miR-71 has been shown to affect a diverse range of pathways, including aging, development, and immune response. However, the exact mechanisms by which miR-71 regulates these pathways are not completely understood. In this paper, we review the identified functions of miR-71 across multiple organisms, including identified gene targets, pathways, and the conditions which affect regulatory action. Additionally, the degree of conservation of miR-71 in the evaluated organisms and the conservation of their predicted binding sites in target 3' UTRs was measured. These studies may provide an insight on the patterns, interactions, and conditions in which miR-71 is able to exert genotypic and phenotypic influence.

Discovery and structure-activity relationship of Morita-Baylis-Hillman adducts as larvicides against dengue mosquito vector, Aedes aegypti (Diptera: Culicidae)

Neglected tropical diseases (NTDs) have become a significant public health problem worldwide, notably the life-threatening dengue hemorrhagic fever borne by the Aedes aegypti mosquito. Thus, mosquito vector control measures remain essential in public health vector surveillance and control to combat Aedes-borne infections. Therefore, a series of MBH adducts were synthesized and assessed towards the fourth instar mosquito larvae, Aedes aegypti, along with the preliminary structure-activity relationship (SAR). Noteworthy, this compound class might be synthetized by an efficient eco-friendly synthesismethod and a rapid route for the synthesis of commercial larvicide through a single synthetic step. The bioassays showed that this compound class is a promising larvicide to control Aedes aegypti mosquito larvae, mainly 3g, with an LC₅₀ of 41.35 µg/mL, which was higher than evaluated positive controls. Nevertheless, it is a viable larvicidalhit candidate for further hit-to-leadproperties optimization of its biphenyl backbone scaffold with enhanced insecticidalbioactivity. Moreover, scanning electron microscopy analysis suggested a disruption of the osmoregulatory/ionoregulatory functions by the complete deterioration of the terminal exoskeleton hindgut and anal papillae. Therefore, this new study shows the larvicidal efficacy of the tested compounds against the Aedes aegypti larvae.

Development, growth and metabolic effects in stage IV lobster (Homarus americanus) following chronic exposure to sediments spiked with commercial formulations of deltamethrin and permethrin

Coastal and estuarine ecosystems are environments heavily influenced by natural and anthropogenic activities. Chemicals used for pest control in agriculture and aquaculture may accumulate in natural coastal environments. Pyrethroids are common pesticides that are used on crops as well as applied to aquaculture pens and then may disperse in the surrounding ocean once treatment is complete. This study observed the sublethal effects of two pyrethroids, permethrin and deltamethrin (within commercially available formulations), on post-larval stage IV American lobster (Homarus americanus) using growth parameters and metabolic rate as indicators. Observed effects on growth parameters were a decrease in size increment and specific growth rate as well as an increase in intermolt period in stage IV lobsters exposed to 100 μg/kg permethrin. No significant differences were found for intermolt period, size increment, or specific growth rate in deltamethrin-exposed stage IV lobsters. Metabolic rates were not significantly different between deltamethrin-exposed and control lobsters, however, this sublethal effect warrants further investigation. Collectively, these results represent the first examination of the sublethal effects of exposure to pyrethroids formulations in post-larval lobsters, highlighting the potential for effects on non-target marine organisms.

Pesticide exposure affects DNA methylation patterns in natural populations of a mayfly

Chemical pollutants derived from agricultural activities represent a major threat to freshwater biota. Despite growing evidence involving epigenetic processes, such as DNA methylation, in response to pesticide contamination in agroecosystems, research on wild populations of non-model species remains scarce, particularly for endemic freshwater arthropods. Using the MethylRAD method, this study investigates whether exposure to pesticide contamination in natural populations of the endemic mayfly A. torrens produces genome wide changes in levels of DNA methylation. From a total of 1,377,147 MethylRAD markers produced from 285 specimens collected at 30 different study sites along the Limarí watershed of north-central Chile, six showed significant differential methylation between populations exposed and unexposed to pesticides. In all cases the effect of pesticides was positive, independent and stronger than the effects detected for other spatial and environmental factors. Only one candidate marker appeared correlated significantly with additional variables, nitrate and calcium levels, which also reflects the impact of agrichemicals and could additionally suggest, to a lower extent, antagonistic effects of mineral salts concentration for this specific marker. These results suggest that the effect of pesticide exposure on methylation levels is apparent at these six MethylRAD markers in A. torrens populations. Such data is challenging to obtain in natural populations and is, for the most part, lacking in ecotoxicological studies. Our study shows that DNA methylation processes are involved in the response to pesticide contamination in populations of the mayfly A. torrens in their natural habitat, and provides new evidence regarding the impact of pesticide contamination and agricultural activities on the endemic fauna of lotic ecosystems.

Contamination Pattern and Risk Assessment of Polar Compounds in Snow Melt: An Integrative Proxy of Road Runoffs

To assess the contamination and potential risk of snow melt with polar compounds, road and background snow was sampled during a melting event at 23 sites at the city of Leipzig and screened for 489 chemicals using liquid chromatography high-resolution mass spectrometry with target screening. Additionally, six 24 h composite samples were taken from the influent and effluent of the Leipzig wastewater treatment plant (WWTP) during the snow melt event. 207 compounds were at least detected once (concentrations between 0.80 ng/L and 75 μg/L). Consistent patterns of traffic-related compounds dominated the chemical profile (58 compounds in concentrations from 1.3 ng/L to 75 μg/L) and among them were 2-benzothiazole sulfonic acid and 1-cyclohexyl-3-phenylurea from tire wear and denatonium used as a bittern in vehicle fluids. Besides, the analysis unveiled the presence of the rubber additive 6-PPD and its transformation product N-(1.3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) at concentrations known to cause acute toxicity in sensitive fish species. The analysis also detected 149 other compounds such as food additives, pharmaceuticals, and pesticides. Several biocides were identified as major risk contributors, with a more site-specific occurrence, to acute toxic risks to algae (five samples) and invertebrates (six samples). Ametryn, flumioxazin, and 1,2-cyclohexane dicarboxylic acid diisononyl ester are the main compounds contributing to toxic risk for algae, while etofenprox and bendiocarb are found as the main contributors for crustacean risk. Correlations between concentrations in the WWTP influent and flow rate allowed us to discriminate compounds with snow melt and urban runoff as major sources from other compounds with other dominant sources. Removal rates in the WWTP showed that some traffic-related compounds were largely eliminated (removal rate higher than 80%) during wastewater treatment and among them was 6-PPDQ, while others persisted in the WWTP.

Presence of selected organochlorine pesticides (OCPs) in sediments and biota of River Satluj, Pakistan: first report

Abstract In the developed countries, the use of OCPs (organochlorine pesticides) has been banned. However, in South Asia several of them are still in use. In Pakistan and India a constant addition of OCPs into the atmosphere has been indicated by various researchers. In this study levels of selected organochlorine pesticide residues were assessed in sediment and biota collected from four (4) water reservoirs (3 Barrages & 1 Siphon) on the River Satluj Pakistan, along 231 miles (372 km) of River stretch which was further divided into 12 sampling sites. It was aimed to find out the levels of organochlorine pesticide (OCPs) residues in sediments and from selected fish species (Labeo rohita, Wallagu attu, Cyprinus carpio) of the River Satluj Pakistan. The Organochlorine residues (seven pesticides) present in samples of sediments and biota were investigated through multi residue method, using Gas Chromatograph (GC-ECD).In the current study, the concentration of DDT, was investigated in Wallago attu (0.786-3.987 ppb), Labeo rohita (0.779-4.355 ppb) and Cyprinus carpio (1.234-5.654 ppb). DDE was also found in Cyprinus carpio (1.244-6.322 ppb), Wallag attu (0.877-4.221 ppb) and Labeo rohita (2.112-5.897 ppb). Aldrin was not observed in Labeo rohita and Wallago attu. Currently, lindane and DDE was found predominately high in the sediments of study area at SZ-4 (Panjnad Barrage) ranging (2.238-8.226 ppb) and (4.234-6.876 ppb), respectively. Heaptachlor was found only at SZ-4 (Panjnad Barrage) from the sediments with concentration ranging (0.032-234 ppb). In short all other residues investigated were found below the MCL (maximum concentration level) in all the compartments of the study area set by various agencies like WHO/FAO- Codex Alimenterious.

Effects of Pesticides on the Survival of Shredder Nectopsyche sp. (Trichoptera) and Leaf Decomposition Rates in Tropical Andes: A Microcosm Approach

Andean streams are becoming increasingly impacted by agricultural activities. However, the potential effects of pesticides on their aquatic biodiversity remain unassessed. In order to address this knowledge gap, we conducted an experiment over 37 days in microcosms to assess the effect of two pesticides commonly used in Ecuador (Engeo and Chlorpyrifos) on the aquatic insect Nectopsyche sp. (Trichoptera: Leptoceridae) at 0, 0.10, 5 and 10 μg L^-1 concentrations. The highest concentration corresponds to the maximum concentration allowed by the Equatorian legislation. We assessed insect mortality every 24 h, with leaf litter decomposition rates of organic matter determined by deploying Andean alder (Alnus acuminata) dry leaf packs in the microcosms. We found significant mortality of Nectopsyche sp. at high concentrations of Chlorpyrifos, whereas leaf litter was not significantly affected by any of the treatments. We conclude that the environmental legislation of Ecuador might not be fully protecting aquatic biodiversity from pesticide pollution. Further studies are needed, especially when considering that the maximum permitted concentration is very likely exceeded in many areas of the country. We also suggest that the maximum permissible values should be reviewed, considering each pesticide individually.

Acute toxicity and teratogenicity of carbaryl (carbamates), tebufenpyrad (pyrazoles), cypermethrin and permethrin (pyrethroids) on the European sea bass (Dicentrarchus labrax L, 1758) early life stages

The toxicity of carbaryl, tebufenpyrad, cypermethrin and permethrin was evaluated in European sea bass Dicentrarchus labrax during the embryonic and larval development using six different concentrations per chemical. The order of the toxicity effectiveness was carbaryl > tebufenpyrad > cypermethrin > permethrin. The larvae were more sensitive to all tested chemicals than embryos. The LC50 of carbaryl, tebufenpyrad, cypermethrin and permethrin was determined as 13.88, 43.96, 92 and 142 ppm and 9.27, 25.67, 48.4 and 72.7 ppm in embryo and larvae, respectively. Furthermore, the tested pesticides exhibited teratogenic effects on D. labrax embryo-larval stages. The observed malformations were coagulation, no spherical egg, unhatched egg, pericardial oedemata, yolk oedemata, lordosis, kyphosis, scoliosis, no eye, cranial deformation and body atrophy. Malformations were induced with 0.5 ppm carbaryl, 10 ppm tebufenpyrad and 50 ppm cypermethrin and permethrin; the highest rates of malformation were noted with 16 ppm carbaryl, 160 ppm tebufenpyrad, 400 ppm cypermethrin and 400 ppm permethrin as 34.5%, 28%, 17.5% and 16%, respectively. A positive correlation between the incidence of malformation and the increase of pesticide concentration was established.

Sublethal exposure to pyriproxyfen does not impair the abilities of the backswimmer Buenoa amnigenus to prey upon Aedes aegypti larvae

Pyriproxyfen is a juvenile hormone analogue that is commonly used to control the immature stages of mosquitoes in both artificial and natural water reservoirs. Recently, concerns have been raised regarding the community effectiveness of pyriproxyfen in preventing vector-transmitted diseases. Such concerns have been based on the unintended effects on non-target organisms and the selection of resistant mosquito populations. This investigation was, therefore, conducted to evaluate the toxicity of pyriproxyfen to Aedes aegypti (Diptera: Culicidae) larvae and the backswimmer Buenoa amnigenus (Hemiptera: Notonectidae), a naturally occurring mosquito larvae predator. We also assessed the abilities of backswimmers exposed to sublethal levels of pyriproxyfen to prey upon mosquito larvae (L2) under three larval densities (3, 6, or 9 larvae/100 mL of water) using artificial containers. Our results revealed that pyriproxyfen killed backswimmers only at concentrations higher than 100 μg active ingredient [a.i.]/L, which is 10 times higher than that recommended for larvicidal field application (i.e, 10 μg a.i./L). The abilities of backswimmers exposed to sublethal levels of pyriproxyfen (100 μg a.i./L) to prey upon mosquito larvae were not affected. Harmful effects on the backswimmer predatory abilities were detected only at concentrations of 150 μg a.i./L and when there was a higher prey availability (i.e., 9 larvae/100 mL of water). Together, our findings indicate that the reduced community effectiveness of this insecticide derives from factors other than its detrimental effects on non-target organisms such as backswimmers.

RNA-Seq and 16S rRNA Analysis Revealed the Effect of Deltamethrin on Channel Catfish in the Early Stage of Acute Exposure

Deltamethrin (Del) is a widely used pyrethroid insecticide and a dangerous material that has brought serious problems to the healthy breeding of aquatic animals. However, the toxicological mechanisms of Del on channel catfish remain unclear. In the present study, we exposed channel catfish to 0, 0.5, and 5 μg/L Del for 6 h, and analyzed the changes in histopathology, trunk kidney transcriptome, and intestinal microbiota composition. The pathological analyses showed that a high concentration of Del damaged the intestine and trunk kidney of channel catfish in the early stage. The transcriptome analysis detected 32 and 1837 differentially expressed genes (DEGs) in channel catfish trunk kidneys after exposure to 0.5 and 5 μg/L Del, respectively. Moreover, the KEGG pathway and GO enrichment analyses showed that the apoptosis signaling pathway was significantly enriched, and apoptosis-related DEGs, including cathepsin L, p53, Bax, and caspase-3, were also detected. These results suggested that apoptosis occurs in the trunk kidney of channel catfish in the early stage of acute exposure to Del. We also detected some DEGs and signaling pathways related to immunity and drug metabolism, indicating that early exposure to Del can lead to immunotoxicity and metabolic disorder of channel catfish, which increases the risk of pathogenic infections and energy metabolism disorders. Additionally, 16S rRNA gene sequencing showed that the composition of the intestinal microbiome significantly changed in channel catfish treated with Del. At the phylum level, the abundance of Firmicutes, Fusobacteria, and Actinobacteria significantly decreased in the early stage of Del exposure. At the genus level, the abundance of Romboutsia, Lactobacillus, and Cetobacterium decreased after Del exposure. Overall, early exposure to Del can lead to tissue damage, metabolic disorder, immunotoxicity, and apoptosis in channel catfish, and affect the composition of its intestinal microbiota. Herein, we clarified the toxic effects of Del on channel catfish in the early stage of exposure and explored why fish under Del stress are more vulnerable to microbial infections and slow growth.

Exposures to deltamethrin on immature Chironomus columbiensis drive sublethal and transgenerational effects on their reproduction and wing morphology

Sublethal exposure to insecticides can trigger unintended responses in non-target insects that may disrupt reproductive and developmental performances of these organisms. Here, we assessed whether sublethal exposure to the pyrethroid insecticide deltamethrin in early life had sublethal and transgenerational effects on the reproduction (i.e., fecundity and fertility) and wing morphology of Chironomus columbiensis, an aquatic insect used as a water quality indicator. We first conducted concentration-response bioassays to evaluate the susceptibility of C. columbiensis larvae to deltamethrin. Our results revealed that deltamethrin toxicity was approximately 7-fold higher when C. columbiensis larvae where exposed to 96 h (LC₅₀ = 0.17 [0.15-0.20] μg/L) than to 24 h (LC₅₀ = 1.17 [0.97-1.43] μg/L). Furthermore, the sublethal exposures (at LC₁ = 0.02 μg/L or LC₁₀ = 0.05 μg/L) of immature C. columbiensis resulted in lower fecundity (e.g., reduced eggs production) and morphometric variation wing shapes. Further reduction in fertility rates (quantity of viable eggs) occurred at deltamethrin LC₁₀ (0.05 μg/L). Almost 80% of the fecundity was recovered with only a single recovery generation; however, two subsequent recovery generations were not sufficient to fully recover fecundity in C. columbiensis. Specimens recovered from 98.5% of wing morphometric variation after two consecutive generations without deltamethrin exposure. Collectively, our findings demonstrates that sublethal exposure to synthetic pyrethroids such as deltamethrin detrimentally affect the reproduction and wing shape of C. columbiensis, but also indicate that proper management of these compounds (e.g., concentration and frequency of application) would suffice for these insects' population recovery.

Simplified Procedures for Managing Insecticidal Waste: A Case Report of KCMUCo-PAMVERC Vector Control Product Testing Facility in North-Eastern Tanzania

Insecticide testing facilities that evaluate a variety of vector control products may generate a large number of hazardous wastes from routine operations. These wastes originate from degraded technical grade materials, sprayed substrates with Indoor Residual Spraying (IRS), and redundant stock or working insecticidal solutions. The washing of Long-Lasting Insecticidal Nets (LLINs) during preparation for laboratory and experimental hut trials also contribute to wastewater with insecticide content. Human and environmental exposure to insecticidal waste can occur during transport, categorization, storage, and disposal, resulting in environmental pollution and potential health effects. Various national and international guidelines have been devised for safe disposal and should be strictly followed to avoid adverse effects on humans or environment. To facilitate proper insecticidal waste management, this paper outlines simple but safe practices derived from international and national guidelines that can be adopted by other similar facilities. National and international policies related to chemical management were reviewed and translated into Standard Operating Procedures (SOPs), training pathways, and manuals. National Environmental Management Council (NEMC) assessed the test facility and recommended disposal procedures. NEMC recommendations were followed to construct the soak pits for liquid waste disposal while chemical transporters and incinerators were contracted for solid waste disposal. An environmental expert was contracted for environmental audit and annual monitoring. Studies and activities at the facility were evaluated for their waste generation index. Safety manual and SOPs on risk assessment, waste management and disposal, handling hazardous materials, health and safety procedures, and chemical usage were written. At KCMUCo-PAMVERC, an annual average of 0.02 and 24.9 cubic meters of liquid waste, which mainly includes a mixture of water, insecticides, and solvents, were generated from laboratory experiments (phase I) and semi-field LLIN experiments (phase II), respectively, while the IRS semi-field experiments generated an annual average of 88 L of liquid waste and 6.3 tons of solid waste. An annual average of 0.18 cubic meters of liquid waste results from other sources, including expired laboratory reagents. Well-translated national and international policies/regulations may be adopted by insecticide test facilities for proper and effective waste disposal.

Effectiveness of a Constructed Wetland with Carbon Filtration in Reducing Pesticides Associated with Agricultural Runoff

The Salinas Valley in Monterey County, California, USA, is a highly productive agricultural region. Irrigation runoff containing pesticides at concentrations toxic to aquatic organisms poses a threat to aquatic ecosystems within local watersheds. This study monitored the effectiveness of a constructed wetland treatment system with a granulated activated carbon (GAC) filter installation at reducing pesticide concentrations and associated toxicity to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus. The wetland was supplied with water pumped from an impaired agricultural and urban drainage. Across five monitoring trials, the integrated system's average pesticide concentration reduction was 52%. The wetland channel and GAC filtration components individually provided significant treatment, and within each, pesticide solubility had a significant effect on changes in pesticide concentrations. The integrated treatment system also reduced nitrate by 61%, phosphate by 73%, and turbidity by 90%. Input water was significantly toxic to C. dubia and H. azteca in the first trial. Toxicity to C. dubia persisted throughout the system, whereas toxicity to H. azteca was removed by the channel, but there was residual toxicity post-GAC. The final trial had significant input toxicity to H. azteca and C. dilutus. The channel reduced toxicity to H. azteca and removed toxicity to C. dilutus. GAC filtration reduced H. azteca toxicity to an insignificant level. There was no input toxicity in the other three trials. The results demonstrate that a wetland treatment system coupled with GAC filtration can reduce pesticide concentrations, nutrients, suspended particles, and aquatic toxicity associated with agricultural runoff.

A worldwide review of currently used pesticides' monitoring in agricultural soils

The adverse effects of pesticides on the agricultural ecosystem have been matter of concern in recent decades. However, attention has mostly been directed to highly persistent chemicals leading to underestimating currently used pesticides. In this review we present an overview of the studies on monitoring currently used pesticides in agricultural soils around the world published in the last 50 years. Furthermore, all data available in the articles has been integrated into one united data set. Finally, an overall meta-analysis on the prepared data set was performed. The result of the meta-analysis has been presented in this article. It was revealed that the occurrence of currently used pesticides in the soil of agricultural regions was alarming in many countries, establishing the need for long-term monitoring programs, especially in regions with intensive agricultural activities, in order to determine real-world currently used pesticides fate and accumulation in the soil.

Isolation of Dibutyl Phthalate-Degrading Bacteria and Its Coculture with Citrobacter freundii CD-9 to Degrade Fenvalerate

Continued fenvalerate use has caused serious environmental pollution and requires large-scale remediation. Dibutyl phthalate (DBP) was discovered in fenvalerate metabolites degraded by Citrobacter freundii CD-9. Coculturing is an effective method for bioremediation, but few studies have analyzed the degradation pathways and potential mechanisms of cocultures. Here, a DBP-degrading strain (BDBP 071) was isolated from soil contaminated with pyrethroid pesticides (PPs) and identified as Stenotrophomonas acidaminiphila. The optimum conditions for DBP degradation were determined by response surface methodology (RSM) analysis to be 30.9 mg/l DBP concentration, pH 7.5, at a culture temperature of 37.2°C. Under the optimized conditions, approximately 88% of DBP was degraded within 48 h and five metabolites were detected. Coculturing C. freundii CD-9 and S. acidaminiphila BDBP 071 promoted fenvalerate degradation. When CD-9 was cultured for 16 h before adding BDBP 071, the strain inoculation ratio was 5:5 (v/v), fenvalerate concentration was 75.0 mg/l, fenvalerate was degraded to 84.37 ± 1.25%, and DBP level was reduced by 5.21 mg/l. In addition, 12 fenvalerate metabolites were identified and a pathway for fenvalerate degradation by the cocultured strains was proposed. These results provide theoretical data for further exploration of the mechanisms used by this coculture system to degrade fenvalerate and DBP, and also offer a promising method for effective bioremediation of PPs and their related metabolites in polluted environments.

An enhanced dispersive liquid–liquid microextraction method based on solidification of floating organic drops for the determination of pyrethroid pesticides in tea infusions

A novel enhanced dispersive liquid–liquid microextraction method based on solidified floating organic solvents containing [P4,4,4,12][PF6] and a hydrophobic solvent mixture for the determination of four pyrethroid insecticides in tea infusions.

Efficacy of bio-rational pesticides for the management of Leucinodes orbonalis Guenee in Rupandehi, Nepal

The field experiment was conducted from March to June of 2017 in field conditions at the Institute of Agriculture and Animal Science (IAAS), Paklihawa Campus, Rupandehi, Nepal to evaluate the efficacy of botanicals, microbial, and chemical insecticide against Leucinodes orbonalis Guenee. We assessed seven treatments including control in randomized complete block design with four replications and two sprays. The treatments evaluated for the management of L. orbonalis were i) Jholmal, 250 ml/l of water ii) Beauveria bassiana (Daman), 4 g/l water iii) Abamectin 5 % (Biotrine), 0.5 ml/l of water iv) Bacillus thuringiensis var. kurstaki (Mahastra), 4 g/l of water v) Emamectin benzoate (Cobra), 0.5 g/l of water vi) Azadirachtin 1500 ppm (Neem Kavach), 5 ml/l of water vii) Control (pure water application). All the treatments applied were found to be superior to the control. The results revealed that the lowest percentage of infested fruit i.e. 57.97% and 34.52% were found at 14 days after the first and second spray of Emamectin benzoate treatment respectively, as well as it was found to be significant over control in both sprays. The marketable yield of plot treated with Emamectin benzoate in eggplant was found to be the highest i.e.7.19 t/ha and 7.13 t/ha which was followed by Neem Kavach with the yield of 6.69 t/ha and 7.06 t/ha and that of control plots was 2.98 t/ha and 2.56 t/ha after first and second spray respectively. Further, our study concluded both marketable yield and Benefit-Cost (BC) ratio of brinjal fruit were the highest under the treatment of Emamectin benzoate followed by Jholmal and Neem Kavach. From this experiment, we concluded that Emamectin benzoate was the most effective treatment for the management of L. orbonalis while Jholmal and Neem Kavach proved to be the best alternative.

Lipidomic response of the entomopathogenic fungus Beauveria bassiana to pyrethroids

Pyrethroids are chemical insecticides that are widely used to control pests. Entomopathogenic fungi are considered environmentally safe alternatives to these compounds. Pyrethroids and entomopathogenic fungi not only co-exist in the environment but can also be applied together in pest control. They are often found in contact with each other, and thus, it seems important to understand their interactions at the cellular level. In this study, we analyzed whether pyrethroids could influence the phospholipid profile of Beauveria bassiana and whether membrane changes are one of the mechanisms by which these fungi adapt to unfavorable environmental conditions. The results of our study revealed that pyrethroids changed the phospholipid profile and increased the cell membrane permeability of B. bassiana, which enabled them to enter and accumulate within the fungal cells, resulting in oxidative stress. Pyrethroids influenced the amount of neutral lipids, caused a decrease in sodium content, and also temporarily lowered the level of the secondary metabolite oosporein in the studied fungi. These findings indicate that the effect of pyrethroids on entomopathogenic fungi may be more complex than originally thought and that lipidomic studies can aid in fully understanding the influence of these chemicals on the mentioned group of fungi.

Detrimental effects of pyriproxyfen on the detoxification and abilities of Belostoma anurum to prey upon Aedes aegypti larvae

Despite being effective in controlling mosquito larvae and a few other target organisms, the application of insecticides into aquatic systems may cause unintended alterations to the physiology or behavioral responses of several aquatic non-target organisms, which can ultimately lead to their death. Here, we firstly evaluated whether the susceptibility of the giant water bug, Belostoma anurum (Hemiptera: Belostomatidae), a predator of mosquito larvae, to pyriproxyfen would be similar to that of its potential prey, larvae of Aedes aegypti (Diptera: Culicidae). Secondly, we recorded the nominal concentrations of pyriproxyfen in water and evaluated whether sublethal exposures would lead to physiological or behavioral alterations on the B. anurum nymphs. We characterized the activities of three major families of detoxification enzymes (i.e., cytochrome P450 monooxygenases, glutathione-S-transferase, and general esterases) and further evaluated the abilities of pyriproxyfen sublethally-exposed B. anurum to prey upon A. aegypti larvae at different prey densities. Our findings revealed that nominal pyriproxyfen concentration significantly decreased (approximately 50%) over the first 24 h. Furthermore, when applied at the concentration of 10 μg a.i./L, pyriproxyfen was approximately four times more toxic to A. aegypti larvae (LT₅₀ = 48 h) than to B. anurum nymphs (LT₅₀ = 192 h). Interestingly, the pyriproxyfen sublethally-exposed (2.5 μg a.i./L) B. anurum nymphs exhibited reduced enzyme activities (cytochrome P450 monooxygenases) involved in detoxication processes and preyed significantly less on A. aegypti larvae when compared to unexposed predators. Collectively, our findings demonstrate that mortality-based pyriproxyfen risk assessments are not always protective of aquatic non-target organisms.

Ixodiphagus hookeri wasps (Hymenoptera: Encyrtidae) in two sympatric tick species Ixodes ricinus and Haemaphysalis concinna (Ixodida: Ixodidae) in the Slovak Karst (Slovakia): ecological and biological considerations

Ixodiphagus endoparasitoid wasps are natural tick enemies that can reduce their abundance. In this study, we investigated the presence of Ixodiphagus hookeri in Haemaphysalis concinna and Ixodes ricinus ticks in the Slovak Karst (southern Slovakia) and analysed the ecological and physiological relationships in the parasitoid-host system. Unfed H. concinna and I. ricinus nymphs harvested from vegetation were fed on rabbits. The engorged specimens were kept at 25 °C and 75% RH until the emergence of the adult wasps. For the first time in Europe, we found the presence of I. hookeri in two species of ticks collected in the same locality and compared their development in these tick species. The prevalence of wasps in H. concinna and I. ricinus during their spring activity was estimated at 10.64% and 27.78%, respectively. The presence of the wasps did not affect the duration of nymph feeding. Engorged wasp-infected ticks achieved higher body mass than non-infected specimens. In both tick species, there were no differences in the length of the development period and the number and sex ratio of adult I. hookeri. The analysed indicators and characteristics of the I. hookeri wasp-tick system can be used in research on tick control.

Multi-biomarker assessment in the giant freshwater prawn Macrobrachium rosenbergii after deltamethrin exposure

Deltamethrin (DM) is a synthetic pyrethroid used for agricultural purposes to control insects. However, its extensive use contaminates the aquatic environment and results in serious health problems in aquatic organisms. Knowledge about the toxic effect of DM in freshwater prawns is limited; therefore, this study aims to assess the toxicity of DM in Macrobrachium rosenbergii based on multiple biomarkers. Four-day acute toxicity tests showed that DM was highly toxic to M. rosenbergii with the 24 h, 48 h, 72 h and 96 h LC₅₀ values to be 1.919, 0.603, 0.539, and 0.449 μg/L, respectively. According to 96 h LC₅₀, prawns were exposed to DM at three concentrations (0.02, 0.08, and 0.32 μg/L) for 4 days, and then moved into fresh water for decontamination to investigate the toxic effect of DM in M. rosenbergii. At low concentration (0.02 μg/L and 0.08 μg/L), DM did not cause obvious histopathological damage to hepatopancreas and gill tissue, while at high concentration (0.32 μg/L), the histopathological harm was serious and the damage did not recover to the initial level after 7-day decontamination. 0.02 μg/L DM exposure did not induce significant changes in most of the biomarkers except the increased lactate dehydrogenase (LDH) activity, lactic acid (LD) level, and the first increased then decreased mRNA expression of immune-related genes, indicating the stimulation of DM on energy production and immunity. 0.08 μg/L and 0.32 μg/L DM exposure resulted in varying degrees of damage on prawns, but overall, their toxic effects showed similar trends based on the biomarkers. Increase in malonaldehyde (MDA) and hydrogen peroxide (H₂O₂) content and decrease in superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity after DM exposure demonstrated the oxidative stress caused by DM. The significantly increased acid phosphatase (ACP), alkaline phosphatase (AKP), LDH activity and LD level indicated hepatopancreatic dysfunction and respiration disruption. The first increased and then decreased expression pattern of immune-related genes indicated the immunosuppression caused by DM. After 7-day decontamination in freshwater, the activity/level of the biomarkers partly recovered. This study revealed the severe toxic effect of DM on Macrobrachium rosenbergii based on multiple biomarkers, providing fundamental knowledge for the establishment of DM toxicity assessment system with proper parameters in freshwater crustaceans.

Pyrethroid bioaccumulation in field-collected insecticide-resistant Hyalella azteca

Wild-type Hyalella azteca are highly sensitive to pyrethroid insecticides and typically do not survive exposure; however, pyrethroid bioaccumulation by insecticide-resistant H. azteca is an important potential risk factor for the transfer of pyrethroids to higher trophic species in aquatic systems. In the current study, four populations of pyrethroid-resistant H. azteca with corresponding sediment samples were sampled throughout the year, and nine-current use pyrethroids (tefluthrin, fenpropathrin, bifenthrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin, esfenvalerate and deltamethrin) were measured. Bifenthrin was detected in every pyrethroid-resistant H. azteca tissue sample, up to 813 ng/g lipid, while cyhalothrin and permethrin were detected in fewer (18 and 28%, respectively) samples. Concurrent sampling of the sediment showed total pyrethroid concentrations exceeding toxic unit thresholds for non-resistant H. azteca survival, and confirmed the ubiquitous presence of bifenthrin at each site and sampling event. Bifenthrin concentrations in H. azteca tended to be higher in samples collected in winter months, and seasonal factors, such as temperature and rainfall, may have contributed to the noted differences in bioaccumulation. Finally, the bifenthrin and permethrin biota-sediment accumulation factors (BSAF) for pyrethroid-resistant H. azteca were similar to the BSAF values for less sensitive invertebrates, and therefore the development of resistance may enable an additional pathway for trophic transfer of pyrethroids in species that would otherwise be too sensitive to survive the exposure.

Cascading effects of insecticides and road salt on wetland communities

Novel stressors introduced by human activities increasingly threaten freshwater ecosystems. The annual application of more than 2.3 billion kg of pesticide active ingredient and 22 billion kg of road salt has led to the contamination of temperate waterways. While pesticides and road salt are known to cause direct and indirect effects in aquatic communities, their possible interactive effects remain widely unknown. Using outdoor mesocosms, we created wetland communities consisting of zooplankton, phytoplankton, periphyton, and leopard frog (Rana pipiens) tadpoles. We evaluated the toxic effects of six broad-spectrum insecticides from three families (neonicotinoids: thiamethoxam, imidacloprid; organophosphates: chlorpyrifos, malathion; pyrethroids: cypermethrin, permethrin), as well as the potentially interactive effects of four of these insecticides with three concentrations of road salt (NaCl; 44, 160, 1600 Cl^- mg/L). Organophosphate exposure decreased zooplankton abundance, elevated phytoplankton biomass, and reduced tadpole mass whereas exposure to neonicotinoids and pyrethroids decreased zooplankton abundance but had no significant effect on phytoplankton abundance or tadpole mass. While organophosphates decreased zooplankton abundance at all salt concentrations, effects on phytoplankton abundance and tadpole mass were dependent upon salt concentration. In contrast, while pyrethroids had no effects in the absence of salt, they decreased zooplankton and phytoplankton density under increased salt concentrations. Our results highlight the importance of multiple-stressor research under natural conditions. As human activities continue to imperil freshwater systems, it is vital to move beyond single-stressor experiments that exclude potentially interactive effects of chemical contaminants.

Detoxification gene expression, genotoxicity, and hepatorenal damage induced by subacute exposure to the new pyrethroid, imiprothrin, in rats

The pyrethroid imiprothrin is widely used worldwide for control of insects in the agriculture and public health sectors. No sufficient information is however available concerning detoxification gene expression, i.e., cytochrome P450 1A2 (CYP1A2) and metallothionein 1a gene, oxidative stress, lipid peroxidation, DNA damage, cytotoxicity, genotoxicity, and organ injury induced by imiprothrin in mammals. This study is designed to explain the mechanism of imiprothrin induced detoxification gene expression, DNA damage, cytotoxicity, genotoxicity, and organ toxicity in male rats. The benchmark dose (BMD) was calculated to find the best sensitive markers to imiprothrin toxicity. Imiprothrin was injected intraperitoneally (i.p.) into male rats once a day for 5 days with doses of 19, 38, and 75 mg/kg body weight (b.wt.). Imiprothrin caused a significant increase in lipid peroxidation and changes in oxidative stress biomarkers in treated rats. Significant dose-dependent changes in the liver and kidney biomarkers were observed. Histopathological alterations were seen in the liver and kidney tissue of male rats. Imiprothrin also significantly increased chromosomal aberrations (CA) and micronuclei in bone-marrow cells, and induced lipid peroxidation, oxidative stress, cytotoxicity, and liver and kidney dysfunction, and damage. Imiprothrin induced DNA damage and over detoxification gene expression of CYP1A2 and metallothionein 1a gene in hepatocytes of male rats. Imiprothrin thus shows clastogenic and genotoxic potential. The mechanism for hepatorenal toxicity and injury, genotoxicity/cytotoxicity of imiprothrin might be due to enhanced lipid peroxidation, and oxidative stress associated with overproduction of free radicals, especially reactive oxygen species, and an imbalance in redox status. From the BMD models, aspartate aminotransferase (AST), total protein, uric acid, superoxide dismutase (SOD), and micronuclei (MPEs) were very sensitive markers to imiprothrin toxicity.

Receptor-binding affinity and larvicidal activity of tetrahydroquinoline-type ecdysone agonists against Aedes albopictus

Tetrahydroquinolines (THQs), a class of nonsteroidal ecdysone agonists, are good candidates for novel mosquito control agents because they specifically bind to mosquito ecdysone receptors (EcRs). We have recently performed quantitative structure-activity relationship (QSAR) analyses of THQs to elucidate the physicochemical properties important for the ligand-receptor interaction. Based on previous QSAR results, here, we newly synthesized 15 THQ analogs with a heteroaryl group at the acyl moiety and evaluated their binding affinity against Aedes albopictus EcRs. We also measured the larvicidal activity of the combined set of previously and newly synthesized compounds against A. albopictus to examine the contribution of receptor-binding to larvicidal activity. Multiple regression analyses showed that the binding affinity and the molecular hydrophobicity of THQs are the key determinants of their larvicidal activity.

Bio-Control of Anopheles Mosquito Larvae Using Invertebrate Predators to Support Human Health Programs in Ethiopia

Mosquitoes have been a nuisance and health threat to humans for centuries due to their ability to transmit different infectious diseases. Biological control methods have emerged as an alternative or complementary approach to contain vector populations in light of the current spread of insecticide resistance in mosquitoes. Thus, this study aimed to evaluate the predation efficacy of selected potential predators against Anopheles mosquito larvae. Potential invertebrate predators and Anopheles larvae were collected from natural habitats, mainly (temporary) wetlands and ponds in southwest Ethiopia and experiments were conducted under laboratory conditions. Optimal predation conditions with respect to larval instar, water volume and number of predators were determined for each of the seven studied predators. Data analyses were carried out using the Poisson regression model using one way ANOVA at the 5% significant level. The backswimmer (Notonectidae) was the most aggressive predator on Anopheles mosquito larvae with a daily mean predation of 71.5 larvae (95% CI: [65.04;78.59]). Our study shows that larval instar, water volume and number of predators have a significant effect on each predator, except for dragonflies (Libellulidae), with regard to the preference of the larval instar. A selection of mosquito predators has the potential to control Anopheles mosquito larvae, suggesting that they can be used as complementary approach in an integrated malaria vector control strategy.

Differences in Bifenthrin and Fipronil Susceptibility Among Invasive Latrodectus spp. (Araneae: Theridiidae) and Nontarget Spiders in Japan

Prompt responses to invasive Latrodectus spiders introduced unintentionally are needed worldwide due to their medical and ecological importance. Latrodectus species are chemically controlled using pyrethroid insecticides despite concerns about the ecological impacts of these compounds on biodiversity/ecosystems. Here, the relative sensitivities (acute toxicity: 48-h LC50) of Latrodectus hasseltii Thorell and Latrodectus geometricus C.L. Koch from Japan to the conventional neurotoxic insecticide bifenthrin (pyrethroid) and a new candidate insecticide, fipronil (phenylpyrazole), were examined. Acute residual toxicity tests of these compounds in two nontarget spiders (Parasteatoda tepidariorum C.L. Koch (Araneae: Theridiidae), Badumna insignis L. Koch (Araneae: Desidae)) were conducted for comparison. To test whether bifenthrin and fipronil toxicities differed among the four spiders, corresponding species sensitivity distributions (SSDs) were compared, and hazardous concentrations were determined. Sensitivity (especially in the nontarget species) was two to four orders of magnitude higher for bifenthrin than for fipronil. The SSD patterns of the two insecticides differed significantly, with the spider communities being more sensitive to bifenthrin than to fipronil. The lethal bifenthrin concentration for Latrodectus may reduce spider populations by over 70-90%. If L. hasseltii (established throughout Japan) is targeted for effective population suppression rather than L. geometricus (with a limited distribution range) using the specified insecticide concentration (LC50 value) for fipronil, less than 20% of spider communities will be impacted. Chemical operations aimed at the effective population management and subsequent eradication of invasive Latrodectus spiders while supporting local biodiversity conservation would benefit from considerations of fipronil dosages and target species sensitivities.

Can Organophosphates and Carbamates Cause Synergisms by Inhibiting Esterases Responsible for Biotransformation of Pyrethroids?

Hydrolysis catalyzed by general esterases (GEs) is the most efficient route for hydrolyzation of pyrethroid insecticides. Organophosphate (OP) and carbamate (CB) insecticides are known to inhibit GEs in addition to acetylcholinesterase (AChE), which is their main target. We hypothesize that synergies can be induced by OPs and CBs when mixed with pyrethroids, due to their inhibition of GE-dependent detoxification of pyrethroids. To test this hypothesis, we conducted mixture toxicity experiments with Daphnia magna using α-cypermethrin (α-cyp) in combination with the noninsecticidal OP tetraisopropyl pyrophosphoramide (iso-OMPA) and five AChE inhibitors diazinon, chlorpyrifos, chlorfenviphos, parathion, and aldicarb. In addition, the in vivo GE activity inhibition was measured for all compounds. Up to 10-fold synergy was found between α-cyp and iso-OMPA, and the degree of synergy correlated linearly with the inhibition of the GE activity. No synergy, however, was found in any of the insecticide mixtures nor was the GE activity inhibited within the nonlethal concentration range tested. It was concluded that the effect of the insecticides on AChE occurred at lower concentrations than their effect on GEs, making the daphnids become immobilized before any synergistic effects on mortality could be observed. The implications of the findings are discussed from a risk assessment perspective.

Eco-friendly Water-Based λ-Cyhalothrin Polydopamine Microcapsule Suspension with High Adhesion on Leaf for Reducing Pesticides Loss

Recently, innovations of nano/microcarrier formulations have been focused on improving application efficiencies and retention time. In this study, a water-based 2.5% λ-cyhalothrin (LC) microcapsule suspension (CS) was developed by orthogonal test with biodegradable and adhesive polydopamine (PDA) microcapsules (MCs) as carriers. The obtained LC-PDA CS had good suspension properties, flow behavior, storage stability, and rheological properties. LC-PDA CS had higher retention, wettability, and decreased rainwater washing out on the leaves than commercial CS. LC-PDA CS displayed higher insecticidal activity against Lipaphis erysimi compared to commercial CS. LC-PDA CS reduced the toxicity of LC to the aquatic organism Danio rerio compared to LC. The above results demonstrated that LC-PDA CS would be eco-friendly water-based pesticides carrier system for prolonging the retention time on target leaf and reducing toxicity to aquatic organisms.

Evaluation of dimethoate toxicity on fertilization and on embryonic development of Paracentrotus lividus (Lamarck, 1816)

Organophosphates are a large class of chemicals with anticholinesterase action insecticides. Dimethoate belongs to the class of organophosphates and it is used for agriculture purpose. Its main toxicological role in animals and humans is the inhibition of the activity of acetylcholinesterase. Although it is not considered genotoxic, carcinogenic and teratogen, there is evidence of increased pup mortality in developmental neurotoxicity studies. Since there is scant published literature about developmental toxicity, we investigated the adverse effects of dimethoate on fertilization and embryonic development in sea urchin (Paracentrotus lividus), a model organism widely used to assess the toxicity of contaminants on environmental matrices; so pesticide residues can be released into the environment, and could affect the health of organisms, including humans. Different solution of dimethoate (4 × 10^-3, 4 × 10^-4, 4 × 10^-5, 4 × 10^-6 and 4 × 10^-7 g/10 ml) have been tested on spermatozoa of P. lividus to evaluate the fertilizing ability of them when we added egg cells untreated. We demonstrated that dimethoate does not interfere with fertilizing ability of spermatozoa but egg cells fertilized by treated spermatozoa showed alterations in the segmentation planes as asymmetric and/or asynchronous cell divisions.

Environmental safety and mode of action of a novel curcumin-based photolarvicide

Aedes aegypti is the vector of important diseases like dengue, zika, chikungunya, and yellow fever. Vector control is pivotal in combating the spread of these mosquito-borne illnesses. Photoactivable larvicide curcumin obtained from Curcuma longa Linnaeus has shown high potential for Ae. aegypti larvae control. However, the toxicity of this photosensitizer (PS) might jeopardize non-target aquatic organisms. The aim of this study was to evaluate the toxicity of this PS to Daphnia magna and Danio rerio, besides assessing its mode of action through larvae biochemical and histological studies. Three PS formulations were tested: PS in ethanol+DMSO, PS in sucrose, and PS in D-mannitol. The LC₅₀ of PS in ethanol+DMSO to D. rerio was 5.9 mg L^-1, while in D. magna the solvents were extremely toxic, and LC₅₀ was not estimated. The PS formulations in sugars were not toxic to neither of the organisms. Reactive oxygen species (ROS) were generated in D. magna exposed to 50 mg L^-1 of PS in D-mannitol, and D. rerio did not elicit this kind of response. D. magna feeding rates were not affected by the PS in D-mannitol. Concerning Ae. aegypti larvae, there were changes in reduced glutathione and protein levels, while catalase activity remained stable after exposure to PS in D-mannitol and sunlight. Histological changes were observed in larvae exposed to PS in sucrose and D-mannitol, most of them irreversible and deleterious. Our results show the feasibility of this photolarvicide use in Ae. aegypti larvae control and its safety to non-target organisms. These data are crucial to this original vector control approach implementation in public health policies.

Effect of Agrochemical Exposure on Schistosoma mansoni Cercariae Survival and Activity

Singular use of activity assays or staining dyes to assess pathogen agrochemical tolerance can underestimate tolerance if pesticides cause sublethal effects. We exposed Schistosoma mansoni cercariae, the aquatic life stage of this trematode that infects humans, to 4 insecticides at 5 concentrations using a 24-h time-to-death assay. We used Trypan blue dye, which stains dead tissue, and activity assays simultaneously to discriminate dead from live but paralyzed individuals. Whereas cypermethrin, deltamethrin, and dimethoate exposure did not affect cercariae at any ecologically relevant concentrations, methamidophos exposure increased survival of cercariae compared with those in the controls. This was because methamidophos-induced paralysis reduced cercarial activity and thus energy expenditures, extending the lifespan of this short-lived parasite that causes human schistosomiasis. These findings highlight that sublethal effects should be considered when pesticide effects on disease are under investigation. Environ Toxicol Chem 2020;39:1421-1428. © 2020 SETAC.

Contamination of neonicotinoid insecticides in soil-water-sediment systems of the urban and rural areas in a rapidly developing region: Guangzhou, South China

Residues and distribution of neonicotinoid insecticides (NEOs) in soil-water-sediment systems of the urban and rural areas of Guangzhou, South China were investigated. A total of 104 soil samples from 7 different functional zones and 29 water/sediment samples from creeks were collected. The results showed that at least one neonicotinoid insecticide was detected in all samples. The summed levels of five target neonicotinoids (∑₅neonics) were in the range of 0.003-229 ng/g dw for soil samples, 7.94-636 ng/L for water samples, and 0.017-31.3 ng/g dw for sediment samples, with a geometric mean of 0.59 ng/g dw, 153 ng/L and 1.11 ng/g dw, respectively. Soils from agricultural areas contained the highest residual NEOs, followed by commercial, traffic, residential, industrial, educational zones and parks. Among the seven different functional zones studied, imidacloprid was the most dominant NEO in the agricultural areas and commercial zones, whereas acetamiprid was dominant in the other five functional zones with different land-use types. Thiamethoxam and acetamiprid were the main NEOs in water and sediment samples collected from 29 creeks. The pollution of NEOs in soils, water and sediments from rural areas was higher than that in the counterparts from urban areas. Residual concentration of NEOs detected in soils, water and sediments showed significant correlations with each other. The distribution of NEOs in soil-water-sediment systems indicated that NEOs tended to concentrate in water, followed by sediments and soils, especially in urban areas. An evaluation of the exposure to the current level of the ∑₅NEOs in Guangzhou suggests a significant risk for aquatic and soil organisms, particularly under chronic exposures. The results of the present study offer valuable data to better understand the contamination and ecological risks of neonicotinoid insecticides in the rapidly developing urbanized region of South China.

The detoxifying effect of Polygonum equisetiforme extracts against dichlorvos (DDVP)-induced oxidative stress and neurotoxicity in the commercial clam Ruditapes decussatus

Effects of Polygonum equisetiforme extracts against dichlorvos were investigated in the commercial clam Ruditapes decussatus. The toxicity of this pesticide was firstly tested in R. decussatus gill and digestive gland tissues using five doses varying from 0.05 to 1 mg/l during 2, 4, and 7 days. Results showed that 0.05 mg/l of DDVP induced oxidative stress and neurotoxicity in R. decussatus after 2 days of exposure. Investigations of the effects of P. equisetiforme extracts in R. decussatus exposed to 0.25 mg/l of DDVP were made in clams receiving three concentrations (0.009, 0.045, and 0.09 g/l) during 4 and 7 days. Antioxidant enzymes SOD and CAT as well as H₂O₂ content and AChE were quantified by colorimetric method. Four days of exposure to DDVP increased SOD and CAT activities and enhances H₂O₂ content. AChE levels decreased considerably following DDVP exposure, although a restoration in the enzyme activity was observed with P. equisetiforme extract (E3 = 0.09 g/l). Overall, P. equisetiforme extract at concentration (E1 = 0.009 g/l) prevents oxidative stress caused by DDVP, while 0.09 g/l of P. equisetiforme extract induced an effect similar to that obtained with DDVP alone. Nevertheless, this concentration was found effective for the restoration of the AChE activity.

A bacterium against the tiger: preliminary evidence of fertility reduction after release of Aedes albopictus males with manipulated Wolbachia infection in an Italian urban area

BACKGROUND

Novel tools are needed to reduce the nuisance and risk of exotic arbovirus transmission associated with the colonization of temperate regions by Aedes albopictus. The incompatible insect technique (IIT) is a population suppression approach based on cytoplasmic incompatibility between males with manipulated endosymbionts and wild females. Here, we present the results of the first field experiment in Europe to assess the capacity of an Ae. albopictus line (ARwP) deprived of its natural endosymbiont Wolbachia and transinfected with a Wolbachia strain from the mosquito Culex pipiens, to sterilize wild females.

RESULTS

We released ∼ 4500 ARwP males weekly for 6 weeks in a green area within urban Rome (Italy) and carried out egg (N = 13 442), female (N = 128) and male (N = 352) collections. Egg (N = 13 783) and female (N = 48) collections were also carried out at two untreated control sites. The percentage of viable eggs during release was, on average, significantly lower in treated sites than in control sites, with the greatest difference (16%) seen after the fourth release. The ARwP to wild male ratio in the release spots between day 3 after the first ARwP male release and day 7 after the last release was, on average, 7:10. Released males survived up to 2 weeks. Approximately 30% of females collected in the release spots showed 100% sterility and 20% showed strongly reduced fertility compared with control sites.

CONCLUSIONS

Results support the potential of IIT as a tool contributing to Ae. albopictus control in the urban context, and stress the need for larger field trials to evaluate the cost-efficacy of the approach in suppressing wild populations. © 2019 Society of Chemical Industry.